Photocatalyst material and process for producing the same

ABSTRACT

A process for producing a photocatalyst material, the photocatalyst material exhibiting highly active photocatalytic action and capable of reducing special odor generated at the time of ultraviolet irradiation. This process comprises the raw photocatalyst material preparation step (P 1 ) of obtaining a photocatalyst material (raw photocatalyst material) being in the state of not bearing any base metal on its surface and the base metal superimposition step (P 3 ) of causing the raw photocatalyst material obtained in the step P 1  to bear base metal fine particles on its surface to thereby obtain the photocatalyst material bearing a base metal. The base metal superimposition step P 3  comprises the solution treatment step (P 31 ) of dipping the raw photocatalyst material in a base metal compound solution according to photoprecipitation, the ultraviolet irradiation step (P 32 ) of irradiating the base metal bearing photocatalyst material obtained in the step P 31  with ultraviolet light and the drying step (P 33 ) of drying the photocatalyst material resulting from the step P 32.

TECHNICAL FIELD

The present invention relates to a photocatalyst material and aproduction method thereof, and particularly, the present inventionrelates to an oxide photocatalyst material that can exert a highphotocatalytic activity at low costs, and can reduce characteristic odorproduced during ultraviolet radiation, and to a production methodthereof.

BACKGROUND ART

An oxide photocatalyst represented by titanium oxide generates electronsin a conduction band and positive holes in a valence band byphotoexcitation, when it is irradiated with light at a wavelength ofenergy not less than its band gap; and decomposes organic matter ornitrogen oxides, which come into contact with the photocatalyst, intowater or carbon dioxide gas by the strong reduction power or the strongoxidative power, and has anti-fouling, deodorization, anti-bacterialfunctions or the like. Although various environmental purificationmethods or devices utilizing such functions have been provided, it isrequired to highly activate the photocatalytic functions of the oxidephotocatalyst itself in order to achieve the further high performanceand high efficiency of the environmental purification methods. On theother hand, the ease of the handling of the oxide photocatalyst and theincorporation in environmental purification devices is desired, andtherefore, it is important to improve both the photocatalytic functionsand the ease of handling.

Particularly, in order to solve the above-described problems in powderyoxide photocatalysts, although a large number of techniques forpreparing oxide photocatalysts, such as a method for vacuum vapordeposition disclosed in Japanese Patent Laid-Open No. 8-266910 and thelike, a sputtering method disclosed in Japanese Patent Laid-Open No.8-309204, and a sol-gel method disclosed in Japanese Patent Laid-OpenNo. 7-100378, have been proposed, no satisfactory techniques from theaspect of high activation of photocatalytic functions have beenobtained.

Techniques for controlling the surface state of a photocatalyst aredisclosed in Japanese Patent Laid-Open No. 9-57912 and the like.Although these are techniques for improving photocatalytic functions byforming a porous silicon oxide film, or by providing irregularities onthe surface of a titanium oxide film or a glass substrate using fineprocessing to widen the area of the surface where the photocatalyst isexposed, or the like, significant improvement has not necessarily beenachieved. There have also been problems in the aspects of costs, such asthe processing of the substrate, the processing of the film, and theinsertion of the underlying layer.

As a technique for controlling crystals that constitute the surfacelayer of a photocatalyst body, although Japanese Patent Laid-Open No.2000-288403 discloses that the surface area where a photocatalyst isexposed is widened and the photocatalytic function is improved by makingthe shape of crystal grains elliptical or semielliptic, the significantimprovement of functions is not necessarily observed, and therefore, anoxide photocatalyst that has the photocatalytic function of higheractivity and excels in convenience of handling is demanded.

Under such situations, with a view to making an oxide photocatalyst moreactive through the control of crystal forms, the present inventorsconducted repeated studies for the preparation of an oxide photocatalystusing various methods, such as a chemical vapor deposition method (CVDmethod) and a physical vapor deposition method (PVD method), and asol-gel method using an organic metal compound or an inorganic metalcompound. As a result, the present inventors found a method wherein acrystal nucleus prepared using various methods, such as a CVD method ora PVD method is put in a sol solution containing an organic metalcompound or an inorganic metal compound, or the sol solution if appliedto the crystal nucleus, cured and heat-treated to grow the crystals oftitanium oxide from the crystal nucleus. Thus, the present inventorsuncovered that photocatalytic functions of high activity were obtainedfrom crystals having a columnar hollow structure, wherein the crystalform of titanium oxide crystals grown from the crystal nucleus, and thecrystal has a hollow structure (hereafter also referred to as columnarhollow crystal). On the basis of the findings, a novel photocatalystmaterial was invented and disclosed (Reference 1: Japanese PatentLaid-Open No. 2002-253975, Reference 2: Japanese Patent Laid-Open No.2002-253964). The photocatalyst material formed of titanium oxidecrystals having the columnar hollow structure is composed mainly of abase portion to be fixed on the surface of a photocatalyst materialsupporting body, and a columnar photocatalyst crystalline body, which isa hollow columnar structure extending from the base portion, and forexample; and has a structure wherein titanium oxide crystals of acolumnar hollow structure are grown from the base portions of crystalnuclei or the like, supported on the photocatalyst material supportingbody, such as various substrates of glass, ceramics, and fibers having anetwork structure (references 1 and 2). Here, a columnar crystal is thegeneric term including all of crystal forms such as prism and cylinder,branched dendrite crystal forms, and the form fused together when aplurality of columnar crystals are grown.

Since the obtained photocatalyst material is fixed on the substrate,which is the supporting body, the problem of scattering as in powderyphotocatalysts can be solved. The time required for reducing theconcentration of acetaldehyde gas of 20 ppm to 1 ppm or less was about50% compared to a powdery photocatalyst, and the rate of decomposingacetaldehyde gas became about twice, and thus, the photocatalyst havingan extremely active that is very effective for the practical applicationto air-cleaning systems and the like could be obtained.

DISCLOSURE OF THE INVENTION

However, a new problem has been actualized only after photocatalystmaterials having high practical usefulness exhibiting extremely highactivity unparalleled in the past. This is the occurrence of somecharacteristic odor from the surface of titanium oxide. Since it wasconfirmed that the odor is similarly produced from conventional powderytitanium oxide by experiments, the odor is considered to be producedwhen a certain substance adsorbed on the surface of titanium oxide isoxidized or reduced by the photocatalytic function, and ischaracteristic in photocatalyst materials. It was also clarified thatthe odor was always produced when ultraviolet rays were radiated to thetitanium oxide photocatalyst, and that the odor was considerably strongimmediately after the radiation of ultraviolet rays. On the other hand,in order to improve the performance of an environmental purificationdevice, and to expand the application field thereof, further improvementof the performance of photocatalysts is extremely important.

The problem to be solved by the present invention is to provide an oxidephotocatalyst material that has higher decomposition performance and canreduce characteristic odor produced during ultraviolet radiation, and amethod for the manufacture thereof. The present inventors studiedrepeatedly about the above problems, and found that the problems couldbe solved by a photocatalyst material supporting a metal or a compoundthereof leading to the completion of the present invention.Specifically, the invention claimed herein is as follows:

(1) A photocatalyst material supported by a photocatalyst materialsupporting body for constituting a photocatalyst body, characterized inthat the particles of either one of a metal or a metallic compound aresupported by said photocatalyst material.

(2) A photocatalyst material supported by a photocatalyst materialsupporting body for constituting a photocatalyst body, characterized inthat the particles of either one of a base metal or a base-metalcompound are supported by said photocatalyst material.

(3) A photocatalyst material supported by a photocatalyst materialsupporting body for constituting a photocatalyst body, characterized inthat the particles of both a base metal and a base-metal compound aresupported by said photocatalyst material.

(4) The photocatalyst material according to (2) or (3), characterized inthat said photocatalyst is titanium oxide, and said base metal orbase-metal compound is at least one of Cu, Fe, Ni, Zn, Co, V, Zr, Mn,Sn, Cr, W, Mo, Nb, Ta, or the compounds thereof.

(5) The photocatalyst material according to any one of (2) to (4),characterized in that said photocatalyst material is a photocatalystmaterial consisting of a base portion to be fixed on the surface of thephotocatalyst material supporting body or a base portion fixed on thesurface of the photocatalyst material supporting body, and a columnarphotocatalyst crystalline body extending from said base portion.

(6) The photocatalyst material according to (5), characterized in thatsaid base portion consists of crystal nuclei or the like, and the insideof said columnar photocatalyst crystalline body has a hollow columnarstructure.

(7) The photocatalyst material according to (6), characterized in that astructure consisting of fine photocatalyst particles in saidphotocatalyst crystalline body.

(8) The photocatalyst material according to any one of (2) to (7),characterized in that when acetaldehyde gas is decomposed using saidphotocatalyst material consisting of a supporting quantity of about 0.1g supported on the photocatalyst material supporting body having acatalyst supporting area of 75 mm×75 mm, the time required for reducingthe acetaldehyde gas concentration in a glass container of a volume of20 liter is 5 minutes or more and 10 minutes or less.

(9) A photocatalyst body comprising a photocatalyst material supportingbody, and the photocatalyst material supported on the photocatalystmaterial supporting body according to any of (2) to (8).

(10) A method for producing a photocatalyst material comprising a rawphotocatalyst material preparing step for obtaining a photocatalystmaterial that supports no base metals or no compounds thereof (hereafterreferred to as “raw photocatalyst material”), and a base-metalsupporting step for supporting the fine particles of a base metal or thecompound thereof on the surface of the obtained raw photocatalystmaterial; characterized in that said base-metal supporting stepcomprises a solution treatment step for implementing treatment, such asimmersing and applying, using a solution of a base-metal compound to theraw photocatalyst material; and a ultraviolet treatment step forreducing and depositing the base metal or the compound thereof on thesurface of the raw photocatalyst material by radiating ultraviolet rayson the photocatalyst material treated in said solution treatment step.

(11) A method for producing a photocatalyst material comprising a rawphotocatalyst material preparing step for obtaining a photocatalystmaterial that supports no base metals or no compounds thereof, and abase-metal supporting step for supporting the fine particles of a basemetal or the compound thereof on the surface of the obtained rawphotocatalyst material; characterized in that said base-metal supportingstep comprises a solution treatment step for implementing treatment,such as immersing and applying, using a solution of a base-metalcompound to the raw photocatalyst material; a drying step for drying thephotocatalyst material treated in said solution treatment step; and aheat treatment step for heat-treating the photocatalyst material treatedin said drying step.

(12) The method for producing a photocatalyst material according to(11), characterized in further comprising, after said heat treatmentstep, a reduction step for reducing fine base metal particles in anoxidized state supported on the surface of said photocatalyst material.

(13) A method for producing a photocatalyst material comprising a rawphotocatalyst material preparing step for obtaining a photocatalystmaterial that supports no base metals or no compounds thereof, and abase-metal supporting step for supporting the fine particles of a basemetal or the compound thereof on the surface of the obtained rawphotocatalyst material; characterized in that said base-metal supportingstep is a chemical vapor deposition step for supporting the fineparticles of a base metal or a compound thereof on the surface of theraw photocatalyst material by a thermal CVD method, a plasma CVD method,or other chemical vapor deposition methods.

(14) A method for producing a photocatalyst material comprising a rawphotocatalyst material preparing step for obtaining a photocatalystmaterial that supports no base metals or no compounds thereof, and abase-metal supporting step for supporting the fine particles of a basemetal or the compound thereof on the surface of the obtained rawphotocatalyst material; characterized in that said base-metal supportingstep is a spray pyrolysis step for pyrolyzing a solution of a base metalcompound by spraying it on the surface of a heated raw photocatalystmaterial, and thereby the base metal or the compound thereof issupported on the surface of the raw photocatalyst material.

(15) A method for producing a photocatalyst material comprising a rawphotocatalyst material preparing step for obtaining a photocatalystmaterial that supports no base metals or no compounds thereof, and abase-metal supporting step for supporting the fine particles of a basemetal or the compound thereof on the surface of the obtained rawphotocatalyst material; characterized in that said base-metal supportingstep comprises a solution treatment step for implementing treatment,such as immersing and applying, using a solution of a base-metalcompound to the raw photocatalyst material; and a reducing agent addingstep for depositing a base metal or the compound thereof on the surfaceof the raw photocatalyst material by adding a reducing agent to thephotocatalyst material treated in said solution treatment step.

(16) A method for producing a photocatalyst material comprising a rawphotocatalyst material preparing step for obtaining a photocatalystmaterial that supports no base metals or no compounds thereof, and abase-metal supporting step for supporting the fine particles of a basemetal or the compound thereof on the surface of the obtained rawphotocatalyst material; characterized in that said base-metal supportingstep is a physical vapor deposition step for supporting the fineparticles of a base metal or a compound thereof on the surface of theraw photocatalyst material by a sputtering method, a vacuum vapordeposition method, or other vapor deposition methods.

Specifically, the present invention can significantly improve thedecomposing performance at low costs, and can reduce or eliminate theoccurrence of characteristic odor when ultraviolet rays are radiated, bysupporting the fine particles of a metal or a compound thereof on thesurface of a photocatalyst material, particularly a photocatalystmaterial composed of a titanium oxide photocatalyst crystal having acolumnar hollow structure previously proposed by the present inventors;and the metal or the like to be used may be a base metal or a compoundthereof, or a precious metal or a compound thereof.

Said titanium oxide photocatalyst crystal is characterized in grown froma crystal nucleus by putting the crystal nucleus in a sol solution of anorganic metal compound or an inorganic metal compound, or by applying asol solution to the crystal nucleus, and curing and heat-treating.Although the titanium oxide crystal having a columnar hollow structureitself has already high activity, the activity can further be improvedby making it support the fine particles of a metal or a oxide thereof,and the decomposing efficiency of harmful organic substances, such asacetaldehyde, can be significantly improved to about twice or morecompared with the photocatalyst material having a columnar hollowstructure, and to about 4 times compared with conventional powderyphotocatalyst.

Specifically, one of typical oxide photocatalyst materials according tothe present invention is a titanium oxide crystal having a columnarhollow structure grown from a crystal nucleus, and having fine particlesof a base metal, such as Cu, or a compound thereof supported on thesurface thereof. The supporting is performed by supporting the basemetal or the like on a photocatalyst material before supporting a basemetal or a compound thereof using a photo-precipitation method, a wetprocess, a PVD method, a CVD method, or a spray pyrolysis method (SPDmethod) or the like.

In the present invention, the columnar shape of a photocatalyst crystalincludes all of prism, cylindrical, rod-like, and other columnar stericstructures; and the columnar crystals include those extending straightin a perpendicular direction, those extending at a slant, thoseextending with curvature, those extending divergingly as branches, andthose wherein a plurality of columnar crystals are grown and fusedtogether in mid-course or the like.

Not only crystal nuclei prepared using a sputtering method, a PVDmethod, such as a vacuum vapor deposition method, or a CVD method, butsingle crystals, polycrystalline bodies and other kinds of crystals canbe widely used. As a crystal nucleus, what cannot be apparentlyrecognized as a nucleus as seen in ordinary chemical reactions, such asa flaw on a substrate, can also be used as an alternative of thenucleus. The columnar crystal structure is characterized in that one ormore columnar crystal is grown on a crystal nucleus, the crystal nucleusand the columnar crystal grown thereon grow in the same orientation; andin a typical structure, the columnar crystal inside has a hollowstructure. A photocatalyst having a columnar crystal structure has ahigher contacting efficiency with the object to be decomposed thanconventional photocatalysts having other crystal forms, and thedecomposition performance is dramatically improved.

Aside from the present invention, the present inventors proposed amethod for improving the decomposition performance over columnar hollowcrystals without removing outer-wall portions by a technique wherein apart of the outer-wall portions of a columnar hollow crystal is removedusing a method, such as dry etching and wet etching to expose theinterior having a hollow structure including a structure composed offine photocatalyst particles to the exterior, in an unpublished patentapplication (Japanese Patent Application No. 2001-392804). By using thecombination of this method and the method for preparing a columnarhollow crystalline photocatalyst material supporting fine particles of aprecious metal of the present invention, the decomposition performanceof the photocatalyst material can further be improved by the synergiceffect.

In this case, as a method for exposing the hollow interior structure ofthe columnar hollow crystalline to exterior, a dry etching method, a wetetching method, and a mechanical method are effective. The dry etchingmethods include physical etching methods and chemical etching methods.The physical etching methods include an ion etching method, a plasmaetching method and the like. The chemical etching methods include a gasetching method. The wet etching method is a method that uses an etchingsolution containing a strong inorganic acid, a strong oxidant, afluoride or the like as the fundamental component. The mechanical methodis a method for exposing the hollow interior structure onto the surfaceby polishing the columnar hollow crystal. By these methods, a part ofthe exterior-wall portion of the columnar hollow crystal can be removed,the hollow interior structure can be exposed to exterior, andphotocatalytic functions of high activity can be obtained.

In the process for preparing a columnar hollow titanium oxide crystals,the thermal conduction rate, which greatly contributes to crystalformation elevates by heat treatment at 15° C./min to 105° C./min, or at20° C./min to 100° C./min, and the hollow interior structure of thecolumnar hollow crystal is exposed by lowering the crystalline densityof the crystals composing the exterior-wall portion of the columnarhollow crystal, and thereby, the high activation of photocatalyticfunctions can be achieved.

The “base-metal supporting process” in the present invention means aprocess for supporting fine particles of a base metal or a compoundthereof on a raw photocatalyst material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram showing the appearance of thephotocatalyst material of the present invention;

FIG. 2 is a conceptual diagram showing the appearance of thephotocatalyst material formed of titanium oxide crystals having acolumnar hollow structure of the present invention;

FIG. 3 is a flow diagram showing the constitution of the method forproducing the photocatalyst material of the present invention using aphoto-precipitation method;

FIG. 4 is a flow diagram showing the process for producing the rawphotocatalyst material having a columnar hollow structure of the presentinvention as an example of the constitution of the process for preparingthe raw photocatalyst material shown in FIG. 3 and the like;

FIG. 5 is a flow diagram showing the constitution of the method forproducing the photocatalyst material of the present invention using awet process.

FIG. 6 is a flow diagram showing the constitution of the method forproducing the photocatalyst material of the present invention using aCVD method;

FIG. 7 is a flow diagram showing the constitution of the method forproducing the photocatalyst material of the present invention using aSPD method;

FIG. 8 is a flow diagram showing the constitution of the method forproducing the photocatalyst material of the present invention using areducing agent; and

FIG. 9 is a flow diagram showing the constitution of the method forproducing the photocatalyst material of the present invention using aPVD method.

Reference numerals and characters used in each figure denote thefollowings:

1 . . . Photocatalyst material supporting body, 2 . . . Base portion(crystal nucleus), 3 . . . Photocatalyst crystalline body (titaniumoxide crystal having a columnar hollow structure), 4 . . . Fineparticles of a metal or a metal compound, 5 . . . Fine particles of abase metal or a base-metal compound, 8, 10 . . . Photocatalyst material,18, 20 . . . Photocatalyst body, P1 . . . Step for preparing rawphotocatalyst material, P3 . . . Step for supporting base metal(photo-precipitation method), P31 . . . Solution treatment step, P32 . .. Ultraviolet radiating step, P33 . . . Drying step, P5 . . . Base metalsupporting step (wet process), P51 . . . Solution treatment step, P52.Drying step, P53 . . . Heat treatment step, P54 . . . Reducing step, P6. . . Step for supporting base metal (CVD method), P7 . . . Step forsupporting base metal (SPD method), P8 . . . Step for supporting basemetal (using reducing agent), P81 . . . Solution treatment step, P82 . .. Step for adding reducing agent, P83 . . . Drying step, P9 . . . Stepfor supporting base metal (PVD method), 41 . . . Gelating step, 42 . . .Curing step, 43 . . . Heat treatment step, S1 . . . Crystal nucleus, S2. . . Sol solution, M3 . . . Prototype of photocatalyst material, M4 . .. Cured prototype, and M5 . . . Raw photocatalyst material

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below in further detailsreferring to the drawings.

FIG. 1 is a conceptual diagram showing the appearance of thephotocatalyst material of the present invention. In the diagram, thephotocatalyst material 8 is a photocatalyst material 8 supported on aphotocatalyst material supporting body 1, such as various substrates,for example, glass, metals, ceramics, or fibers having a networkstructure, for composing a photocatalyst body 18, and fine particles ofat least one of a metal or a metal compound are supported on thephotocatalyst material 8. FIG. 1 is a conceptual diagram, and the sizeof the fine particles 4 of a metal or a compound thereof is exaggeratedcompared with the photocatalyst material 8, and the distribution statethereof is also conceptually shown.

Referring to the diagram, the fine particles 4 include (a) the case offine particles of a specific metal alone, (b) the case of fine particlesof a specific compound, such as an oxide of a metal, alone, and (c) thecase of fine particles of a specific single metal and a specificcompound, such as an oxide of the metal; and the case where differentkinds of metals and different kinds of metal compounds are mixed in anymixed states is also included. Therefore, as an example of the case (c),the case where both fine particles of Pt and PtCl₂, which is thechloride thereof are mixed and supported is also included as anembodiment of the present invention.

Referring to the diagram, the photocatalyst material 8 of the presentinvention is supported on a photocatalyst material supporting body 1 tocompose a photocatalyst body 18, and can be a constitution wherein fineparticles 4 of at least one of a base metal or a base metal compound aresupported on the photocatalyst material 8. Therefore, as fine particles4, for example, only Cu can be supported, only CuO, which is the oxidethereof, can be supported, or the mixture of these can also besupported.

Referring to the diagram, the photocatalyst material 8 of the presentinvention is supported on a photocatalyst material supporting body 1 tocompose a photocatalyst body 18, and can be a constitution wherein amixture of fine particles 4 of both a base metal and a compound of thebase metal. As the photocatalyst, titanium oxide can be used; and as thebase metal or the like, at least one of Cu, Fe, Ni, Zn, Co, V, Zr, Mn,Sn, Cr, W, Mo, Nb, Ta, or the compound thereof can be used. Therefore,for example, the constitution wherein the mixture of both Cu and CuO,which is the oxide thereof, is supported can be used as the fineparticles 4. For example, as Ni and V₂O₅, different elemental substancesand compounds can be optionally combined and supported.

Each photocatalyst material 8 of the present invention described usingFIG. 1 can constitute a photocatalyst body 18 of a form easy to handle,by being supported on a photocatalyst material supporting body 1, suchas various substrates, for example, glass, metals, ceramics, or fibershaving a network structure.

In FIG. 1, the photocatalyst material 8 of the present invention isfixed on the surface of a photocatalyst material supporting body 1, andhas a state wherein the fine particles 4 of a metal such as Cu, or thelike are supported. By using the photocatalyst material 8 thusconstituted to support the fine particles 4 of a metal or the like, theoccurrence of characteristic odor due to ultraviolet radiation isreduced, or the occurrence of the odor is eliminated, when photoexcitation by ultraviolet rays is performed to obtain a photocatalyticeffect. Although the effect to reduce the occurrence of odor iseffectively observed when a precious metal, such as Pt, is used, theeffect can be more significantly functioned by a base metal, such as Cu,or a compound thereof.

When the fine particles 4 of a metal or the like are constituted so thatthe particle diameters thereof become smaller, the decomposition ofharmful organic substances, such as acetaldehyde, is accelerated, andthe decomposition performance is improved.

FIG. 2 is a conceptual diagram showing the appearance of thephotocatalyst material formed of titanium oxide crystals having acolumnar hollow structure of the present invention. In the diagram, thephotocatalyst material 10 has a major constitution wherein thephotocatalyst material 10 is composed of a base portion 2 to be fixed onthe surface of the photocatalyst material supporting body 1, or fixed onthe surface of the photocatalyst material supporting body 1, and acolumnar photocatalyst crystal body 3 extending from the base portion 2;it is supported on a photocatalyst material supporting body 1, such asvarious substrates, for example, glass, metals, ceramics, or fibershaving a network structure to constitute a photocatalyst body 20; andfine particles 5 of at least either one of a base metal or a base-metalcompound is supported. FIG. 2 is a conceptual diagram, and the size ofthe fine particles 5 of a base metal or a compound thereof isexaggerated compared with the photocatalyst material 10, and thedistribution state thereof is also conceptually shown.

Therefore, as fine particles 5, for example, only Cu can be supported,or only CuO, which is the oxide thereof, can be supported, or themixture of these can also be supported.

Referring to the diagram, the fine particles 4 of a metal or the likesupported on the photocatalyst material 8 of the present invention canbe the fine particles of a base metal or a base-metal compound. As thephotocatalyst, titanium oxide can be used; and as the base metal or thelike, at least one of Cu, Fe, Ni, Zn, Co, V, Zr, Mn, or the compoundthereof can be used. Specifically, the photocatalyst material 10 of thepresent invention has a structure wherein a columnar titanium oxidecrystal is grown from the base portion 2 as a photocatalyst materialcrystal body 3, such as a crystal nucleus supported, for example, on thephotocatalyst material supporting body 1; and the precious metal fineparticles 5 of Cu or the like are supported on the surfaces of the baseportion 2 and the photocatalyst material crystal body 3.

Referring to the diagram, the photocatalyst material 10 can beconstituted so that the base portion 2 is composed of a crystal nucleusor the like, the photocatalyst material crystal body 3 has a hollowcolumnar structure (hereafter also referred to as “columnar hollowstructure”), and a structure 6 consisting of photocatalyst particles(not shown) (hereafter also referred to as “crystal grains”) are presentin the photocatalyst material crystal body 3.

As the crystal nucleus, not only the crystal nucleus prepared using asputtering method, a PVD method, such as a vacuum vapor depositionmethod, or a CVD method, but any kinds of single crystals,polycrystalline bodies, powders, ceramics, thermal oxide films of ametal, and anodized films can also be used. Also as the crystal nucleus,what cannot be apparently recognized as a nucleus as seen in ordinarychemical reactions, such as a portion on the substrate but having adifferent state from the substrate, for example, a flaw on the substrateor the protrusion of foreign matter, can also used as the alternative ofthe nucleus. The columnar crystal structure is characterized in that oneor more columnar crystal is grown on a crystal nucleus, the crystalnucleus and the columnar crystal grown thereon grow in the sameorientation; and in a typical structure, inside of the columnar crystalhas a hollow structure.

Each photocatalyst material 10 of the present invention described usingFIG. 2 can constitute a photocatalyst body 20 of an easy-to-handle form,by being supported on a photocatalyst material supporting body 1, suchas various substrates, for example, glass, metals, ceramics, or fibershaving a network structure.

In FIG. 2, the photocatalyst material 10 of the present invention hasthe structure wherein the photocatalyst material 10 is fixed on thesurface of the photocatalyst material supporting body 1 at the baseportion 2, and fine particles 5 of a base metal or the like, such as Cu,are supported on the surfaces of the base portion 2 and thephotocatalyst crystal body 3 extending from the base portion 2. Althoughthe surface area of the photocatalyst crystal body 3 is widened bytaking a columnar structure, and the photocatalytic functions havealready been highly active, the efficiency of decomposing harmfulorganic substances, such as acetaldehyde, is further elevated bysupporting the fine particles 5 of a base metal or the like on thesurface thereof, and about two-fold decomposition efficiency can beobtained compared with the case where no fine particles of a base metalor the like are supported.

For example, in the photocatalyst material 10 of the present invention,when acetaldehyde gas is decomposed using the photocatalyst material 10constituted using a supported quantity of about 0.1 g of photocatalystsupported on a photocatalyst material supporting body having a catalystsupporting area of 75 mm×75 mm, the time required for reducing theconcentration of acetaldehyde gas in a glass container of a volume of 20L from 20 ppm to 1 ppm or less can be shortened to 10 minutes or less,or to 6 minutes depending to the constitution.

In the photocatalyst material using titanium oxide of a columnar hollowstructure according to the present invention, even if no fine particlesof a base metal or the like are supported, since a concentration of 1ppm or less can be achieved in about 15 minutes, which requires about 30minutes by conventional powdery photocatalyst, the decompositionefficiency under the above conditions is about twice; and a considerableimprovement of the decomposition efficiency can be achieved; however,the present invention wherein the fine particles of a base metal or thelike exhibits decomposing performance further exceeding this.Specifically, when the photocatalyst material of the present inventionis compared with a conventional powdery photocatalyst, the time requiredfor decomposition is shortened to about one-fourth to one-fifth, andabout 4 to 5 times decomposition efficiency can be obtained,significantly improving the decomposing performance.

By constituting the fine particles 5 of a base metal or the like so thatthe particle diameter thereof becomes smaller, the decomposition ofharmful organic substances, such as acetaldehyde is accelerated, and thedecomposing performance is improved.

The reason why photocatalytic functions are highly activated bysupporting the fine particles of a metal or the like on a titanium oxidephotocatalyst is that excited electrons are collected and pooled in theconduction band by the absorption of excitation light to thephotocatalyst, and simultaneously, positive holes move toward harmfulorganic substances adsorbed on the surface of the photocatalyst,creating the state wherein the probability of recombination ofelectron-hole pairs is compellingly reduced. Specifically, by thecreation of a charge separation state of electron-hole pairs, therecombination thereof is suppressed, and the photocatalytic reaction byambient oxygen and positive holes, and the oxidization and decompositionof the harmful organic substances are accelerated, achieving theelevation of the sensitivity of the photocatalytic activity.

Referring to the diagram, since the photocatalyst material 10 isconstituted so as to support the fine particles 5 of a metal or thelike, when photoexcitation is performed using ultraviolet rays forobtaining the photocatalytic effect, the production of characteristicodor due to the ultraviolet radiation is reduced, or the production ofodor is eliminated. Although the effect of reducing the production ofodor is effectively recognized even when a precious metal, such as Pt,is used, the effect is more significantly obtained by the use of a basemetal, such as Cu, or a compound thereof.

FIG. 3 is a flow diagram showing the constitution of the producingmethod using a photo-precipitation method as one of the methods forproducing the photocatalyst material of the present invention. In thediagram, the method for producing a photocatalyst material of thepresent invention comprises a raw photocatalyst material preparing stepP1 for obtaining a photocatalyst material that supports no base metalsor the like, and a base-metal supporting step P3 for supporting the fineparticles of a base metal or the like on the surface of the obtainedphotocatalyst material; the base-metal supporting step P3 comprises asolution treatment step P31 for implementing treatment, such asimmersing and applying, using a solution of a base-metal compound to thephotocatalyst material; and a ultraviolet treatment step P32 forreducing and depositing the base metal or the like on the surface of theraw photocatalyst material by radiating ultraviolet rays on thephotocatalyst material treated in the solution treatment step P31.

Referring to the diagram, after the ultraviolet treatment step P32, adrying step P33 for drying the photocatalyst material supporting a basemetal or the like by the step P32 can be provided.

In the method for producing a photocatalyst material using aphoto-precipitation method of the present invention shown in thediagram, a photocatalyst material in the state wherein a base metal orthe like is not yet supported on the surface (raw photocatalystmaterial) is obtained in the raw photocatalyst material preparing stepP1, and then, in the base-metal supporting step P3, the fine particlesof a base metal or the like are supported on the surface of the rawphotocatalyst material obtained in the step P1. A treatment, such asimmersing or applying using a solution of a base-metal compound, isperformed to the raw photocatalyst material in the solution treatmentstep P31 in the base-metal supporting step P3, and then, in theultraviolet treatment step P32, ultraviolet rays are radiated onto thephotocatalyst material treated in the solution treatment step P31, andthe base material or the like is reduced, deposited and supported on thesurface of the photocatalyst material. Furthermore, in the drying stepP33, the photocatalyst material supporting the base material or the likeis dried, and the photocatalyst material supporting the fine particlesof a base metal or the like of the present invention is produced.

Through the ultraviolet treatment step P32, the fine particles of a basemetal or the like supported on the surface of the photocatalyst materialin the solution treatment step P31 are reduced, the decompositionefficiency of harmful organic substances can be improved, and theperformance of photocatalytic functions can be elevated. In addition,the production of the characteristic odor during ultraviolet radiationcan be reduced, or the production thereof can be eliminated.

FIG. 4 is a flow diagram showing the process preparing the rawphotocatalyst material having a columnar hollow structure as an exampleof the constitution of the raw photocatalyst preparing step P1 shown inFIG. 3. In FIG. 4, the process for producing a raw photocatalystmaterial having a columnar hollow structure is mainly constituted of agelating step 41, wherein a crystal nucleus S1 to be the base portion ofa photocatalyst material is dipped in a sol solution S2 containing anorganic metal compound or an inorganic metal compound, or a sol solutionS2 containing an organic metal compound or an inorganic metal compoundis applied to a crystal nucleus S1 to be the base portion of aphotocatalyst material, to obtain the prototype M3 of the photocatalystmaterial by gelation; a curing step 42 for drying and curing theprototype M3 obtained by the gelating step 41 to obtain a curedprototype M4; and a heat-treatment step 43 for heat-treating the curedprototype M4 to obtain a raw photocatalyst material M5 having aphotocatalyst crystal body of a columnar structure or a columnar hollowstructure.

Referring to the diagram, according to the gelating step 41, the crystalnucleus S1 to be the base portion of a photocatalyst material is dippedin a sol solution S2 containing an organic metal compound or aninorganic metal compound, or a sol solution S2 containing an organicmetal compound or an inorganic metal compound is applied to a crystalnucleus S1 to be the base portion of a photocatalyst material, to obtainthe prototype M3 of the photocatalyst material by gelation; next,according to the curing step 42, the prototype M3 obtained by thegelating step 41 is dried and cured to obtain a cured prototype M4; andaccording to the heat-treatment step 43, the cured prototype M4 isheat-treated to obtain a raw photocatalyst material M5 having aphotocatalyst crystal body of a columnar structure or a columnar hollowstructure.

FIG. 5 is a flow diagram showing the constitution of the method forproducing the photocatalyst material of the present invention using awet process. Referring to the diagram, the producing method comprises araw photocatalyst material producing step P1 for obtaining aphotocatalyst material supporting no base material or the like; and abase-metal supporting step P5 for supporting the fine particles of abase metal or the like on the surface of the raw photocatalyst materialobtained in the step P1. The base-metal supporting step P5 isconstituted by a solution treatment step P51 for implementing treatment,such as immersing or applying, using a solution of a base-metal compoundto the raw photocatalyst material; a drying step P52 for drying thephotocatalyst material treated in the solution treatment step P51; and aheat-treatment step P53 for heat-treating the photocatalyst materialtreated in the drying step P52.

Referring to the diagram, in the producing method, a reduction step P54for reducing the fine particles of a base metal in an oxidized statesupported on the surface of the photocatalyst material can be providedafter the heat-treatment step P53. By using the steps shown in FIG. 4 asthe raw photocatalyst material producing step P1, a photocatalystmaterial having a columnar hollow structure can be produced, and can beused as a raw photocatalyst material.

Referring to the diagram, in the method for producing a photocatalystmaterial using a wet process of the present invention, although aphotocatalyst material in the state wherein a base metal or the like hasnot yet been supported on the surface can be obtained in the rawphotocatalyst material producing step P1, and then, the fine particlesof a base metal or the like are supported on the surface of the rawphotocatalyst material obtained in the step P1 in the base-metalsupporting step P5, a treatment using the solution of a base-metalcompound, such as immersing or applying, is implemented to the rawphotocatalyst material in the solution treatment step P51 in thebase-metal supporting step P5, the photocatalyst material treated in thesolution treatment step P51 is dried in the drying step P 52, and then,the photocatalyst material treated in the drying step P 52 isheat-treated in the heat-treatment step P53 to produce the photocatalystmaterial supporting the fine particles of a base metal or the like ofthe present invention. Specifically, the decomposition efficiency ofharmful organic substances can be improved, and the high performance ofphotocatalytic functions can be achieved. In addition, the production ofcharacteristic odor can be reduced, or a photocatalyst material withoutthe production thereof can be produced.

Referring to the diagram, in this producing method, the fine particlesof a base metal in an oxidized state supported on the surface of thephotocatalyst material are reduced in the heat-treatment step P53following the reduction step P54.

FIG. 6 is a flow diagram showing the constitution of the method forproducing the photocatalyst material of the present invention using aCVD method. Referring to the diagram, this producing method comprises araw photocatalyst material producing step P1 for obtaining a rawphotocatalyst material, and a base-metal supporting step P6 forsupporting the fine particles of a base metal or the like on the surfaceof the raw photocatalyst material obtained in the step P1; and thebase-metal supporting step P6 has the constitution to be a chemicalvapor deposition step for supporting the fine particles of a base metalor the like on the surface of the raw photocatalyst material using athermal CVD method, a plasma PVD method or other chemical vapordeposition methods. By using the above-described step shown in FIG. 4 asthe raw photocatalyst material producing step P1, a photocatalystmaterial having a columnar hollow structure can be produced, and thiscan be used as a raw photocatalyst material.

Referring to the diagram, in the method for producing a photocatalystmaterial of the present invention using a CVD method, although a rawphotocatalyst material is obtained in the raw photocatalyst materialproducing step P1, and in the base-metal supporting step P6, the fineparticles of a base metal or the like are supported on the surface ofthe raw photocatalyst material obtained in the step P1, by a chemicalvapor deposition method, which is the base-metal supporting step P6, thefine particles of a base metal or the like are supported on the surfaceof the raw photocatalyst material, and a photocatalyst materialsupporting the fine particles of a base metal or the like of the presentinvention can be produced.

FIG. 7 is a flow diagram showing the constitution of the method forproducing the photocatalyst material of the present invention using aSPD method. Referring to the diagram, this producing method comprises araw photocatalyst material producing step P1 for obtaining a rawphotocatalyst material, and a base-metal supporting step P7 forsupporting the fine particles of a base metal or the like on the surfaceof the obtained raw photocatalyst material; and the base-metalsupporting step P7 has the constitution to be a spray pyrolysis step forspraying a solution of a base-metal compound onto the surface of theheated photocatalyst material, whereby the base metal or the like issupported on the surface of the raw photocatalyst material.

Referring to the diagram, in the method for producing the photocatalystmaterial of the present invention using a SPD method, a rawphotocatalyst material is obtained in the raw photocatalyst materialproducing step P1, and in the base-metal supporting step P7, a solutionof a base-metal compound is sprayed onto the surface of the heatedphotocatalyst material, and is thermally decomposed, whereby the basemetal or the like is supported on the surface of the raw photocatalystmaterial, and a photocatalyst material supporting the fine particles ofa base metal or the like of the present invention can be produced.

FIG. 8 is a flow diagram showing the constitution of the method forproducing the photocatalyst material of the present invention using areducing agent. Referring to the diagram, this producing methodcomprises a raw photocatalyst material producing step P1 for obtaining araw photocatalyst material, and a base-metal supporting step P8 forsupporting the fine particles of a base metal or the like on the surfaceof the obtained raw photocatalyst material; and a base-metal supportingstep P8 has the constitution to be a solution treatment step P81 forimplementing a treatment using the solution of a base-metal compound,such as immersing or applying, to the raw photocatalyst material, and areducing-agent adding step P82 for depositing a base metal or the likeon the surface of a raw photocatalyst material by adding a reducingagent to the photocatalyst material treated in the solution treatmentstep P81. After the reducing-agent adding step P82, a drying step P83for drying the photocatalyst material treated in the step P82 can beprovided.

Referring to the diagram, in the method for producing a photocatalystmaterial of the present invention using a reducing agent, a rawphotocatalyst material is obtained in the raw photocatalyst materialproducing step P1, and a treatment using the solution of a base-metalcompound, such as immersing or applying, is implemented to the rawphotocatalyst material in the solution treatment step P81 in thebase-metal supporting step P8, then in the reducing-agent adding stepP82, a reducing agent is added to the photocatalyst material treated inthe solution treatment step P81 to deposit and support the base metal orthe like on the surface of the raw photocatalyst material, and aphotocatalyst material supporting a base metal or the like of thepresent invention is produced. When the drying step P83 is provided, thephotocatalyst material treated in the reducing-agent adding step P82 isdried to be a photocatalyst material supporting a base metal or the likeof the present invention.

FIG. 9 is a flow diagram showing the constitution of the method forpreparing the photocatalyst material of the present invention using aPVD method. Referring to the diagram, this producing method comprises araw photocatalyst material producing step P1 for obtaining a rawphotocatalyst material, and a base-metal supporting step P9 forsupporting the fine particles of a base metal or the like on the surfaceof the obtained raw photocatalyst material; and the base-metalsupporting step P9 has the constitution to be a physical vapordeposition step for supporting the fine particles of a base metal or thelike on the surface of the raw photocatalyst material by a sputteringmethod, a vacuum vapor deposition method, or other PVD methods.

Referring to the diagram, in the method for producing a photocatalystmaterial of the present invention using a reducing agent, a rawphotocatalyst material is obtained in the raw photocatalyst materialproducing step P1, and in the base-metal supporting step P9, the fineparticles of the base metal or the like on the surface of the rawphotocatalyst material by a sputtering method, a vacuum vapor depositionmethod, or other PVD methods, and a photocatalyst material supporting abase metal or the like of the present invention is produced.

As specific examples for supporting Cu on a photocatalyst materialproduced using the producing method of the present invention, examplesof each step using the above-described wet process, PVD method andphoto-precipitation method will be described. In the wet process, aconventionally developed raw photocatalyst material recorded as acolumnar titanium oxide photocatalyst is dipped in an aqueous solutionof copper nitrate (Cu(NO₃)₂.3H₂O), dried at 150° C. for 60 minutes,heat-treated in an atmosphere at 420° C. for 120 minutes, and thenselectively subjected to a hydrogen reducing treatment to produce aCu-supporting columnar titanium oxide photocatalyst. Comparing with thecolumnar titanium oxide photocatalyst, which is the starting material,this exhibits about twice decomposition performance, and in addition,characteristic odor produced during the photocatalytic reaction isreduced.

On the other hand, in the PVD method, fine Cu particles are supported ona columnar titanium oxide photocatalyst by a sputtering method, and aCu-supporting columnar titanium oxide photocatalyst is produced.Comparing with the columnar titanium oxide photocatalyst, which is thestarting material, this exhibits about twice decomposition performance,and in addition, characteristic odor produced during the photocatalyticreaction is reduced.

An example of the methods for producing a photocatalyst material havinga columnar structure on which Cu is supported using aphoto-precipitation method will be described in detail.

<1> Production of conventionally developed raw photocatalyst materialrecorded as columnar titanium oxide photocatalyst, namely production ofcrystal nucleus and columnar hollow titanium oxide photocatalyst.

A non-alkali glass or a silica-fiber filter (manufactured by AdvantechCo. Ltd., QR-100) subjected to cleaning treatment using a neutraldetergent, iso-propyl alcohol and pure water is used as a substrate, andon the surface of the substrate, a titanium oxide crystal having acolumnar hollow structure on the crystal nucleus is formed by puttingthe crystal nucleus into a sol solution consisting of an organic metalcompound, or by applying the sol solution to the crystal nucleus, andcuring and heat-treating it, to make them a titanium oxide substrate anda titanium oxide filter, respectively. The catalyst-supporting area is75 mm×75 mm, and the titanium oxide supporting quantity is about 0.1 g.In the following examples, the same catalyst-supporting area and thetitanium oxide supporting quantity are also used.

As an example of the methods for preparing s sol solution consisting ofan organic metal compound, 35 g of butanediol, 0.4 g of water and 0.5 gof nitric acid are mixed to be a solution, 5 g of titaniumtetraisopropoxide (TTIP) is dropped into the solution while stirring,and the solution is stirred for 4 hours at normal temperature to obtainthe sol solution.

In thus obtained sol solution, a crystal nuclei prepared using variouspreparation method are dipped, or the sol solution obtained as describedabove is applied to the crystal nuclei prepared on a titanium oxidesubstrate or a titanium oxide filter using various preparation method,and the sol solution is dried, cured and heat-treated to form a titaniumoxide crystal of the crystal nuclei. Curing is performed in a dryerunder the conditions of an attained temperature of 150° C. to 200° C.and a retention time of 2 hours. The heat treatment is performed in anelectric furnace under the conditions of elevated temperature 10°C./min, an attained temperature of 500° C. to 600° C. and a retentiontime of 2 hours.

Among the preparations of crystal nuclei using various preparationmethods, a method for preparing a titanium oxide crystal using an SPDmethod follows the method described in an unpublished patent application(Japanese Patent Application No. 2001-181969 and the like) by thepresent inventors, and the titanium oxide crystal is prepared asfollows. Specifically, the material solution is prepared by addingacetyl acetone (referred to as Hacac) to TTIP in a mol ratio(Hacac/TTIP) of 1.0, diluting this with isopropyl alcohol and stirring.The film forming using a spray pyrolysis (SPD) apparatus (manufacturedby Make, YKII) is performed under the conditions of a pressure of 0.3MPa, a spray quantity of 1.0 ml/sec, a spray time of 0.5 ml/spray, asubstrate temperature of 450° C., and number of spray of 200. Accordingto the surface observation using a scanning electron microscope (SEM),the titanium oxide crystal film produced using the SPD method is atitanium oxide crystal film composed of crystals having the sizes of 30nm to 100 nm, and can be obtained as a raw photocatalyst material of thepresent invention.

<2> Base-Metal Supporting <1> Material Solution of Base Metal to beSupported

When copper nitrate trihydrate is used as a Cu compound, it is dilutedwith water to prepare an aqueous solution of a concentration of 2×10⁻⁵mol/l. Further, 10% by weight of ethanol is added thereto to form a Cumaterial solution. The aqueous solution of copper nitrate can be usedfrom the concentration of about 2×10⁶ mol/l or higher. As theconcentration of the solution is lower, the particle diameter of themetal supported on the surface of the photocatalyst material can bereduced, and the improvement of the photocatalytic performance can beexpected.

<3> Base-Metal Supporting <2> Photo-Precipitation Step

A titanium oxide filter or the like is dipped in a Cu material solution,and ultraviolet rays are radiated thereon. By this operation, Cu ions inthe Cu material solution are reduced due to the reducing function of thephotocatalyst, and deposited on the surface of titanium oxide. Besidesthe dipping treatment, Cu can be supported by radiating ultraviolet raysafter the Cu material solution is applied to the surface of titaniumoxide using a spray method or the like.

<4> Base-Metal Supporting <3> Drying Step

After Cu is supported on the titanium oxide filter, the titanium oxidefilter is washed with pure water, and the photocatalyst material isdried at 150° C. for 1 hour.

By the above step, fine Cu particles are supported, and a Cu-supportingcolumnar titanium oxide photocatalyst can be produced. Comparing withthe columnar titanium oxide photocatalyst, which is the startingmaterial, this exhibits about twice decomposition performance, and inaddition, characteristic odor produced during the photocatalyticreaction is reduced.

EXAMPLES

The test results will be described below using examples and comparativeexamples; however, the present invention is not limited to the followingexamples.

The methods for preparing each of examples and comparative examples, andthe like are collectively shown in Table 1. TABLE 1 KIND OF TITANIUMPRESENCE AND ABSENCE OF OXIDE BASE METAL SUPPORTING PHOTOCATALYST ANDMETHOD OF SUPPORTING Example Columnar hollow Photo-precipitation method1 titanium oxide Immersing in Cu material photocatalyst solution → Blacklight radiation → Drying (150° C., 1 hr) Example Columnar hollow Wetprocess 2 titanium oxide Immersing in aqueous solution photocatalyst ofcupper nitrate → drying (150° C., 1 hr) → Heat treatment (450° C., 1 hr,in air) → Reduction treatment (450° C., 2 hr, in H₂—Ar environment)Example Columnar hollow Physical vapor deposition 3 titanium oxidemethod Supporting Cu by photocatalyst sputtering method Compar- Columnarhollow No Cu supporting ative titanium oxide Example photocatalyst 1Compar- Powdery titanium No Cu supporting ative oxide Examplephotocatalyst 2

Example 1 Cu-Supporting Photocatalyst Material Prepared byPhoto-Precipitation Method

Using the above-described photo-precipitation method, Cu was supportedon a columnar hollow titanium oxide photocatalyst material to prepare atitanium oxide filter. It was confirmed by SEM observation that fine Cuparticles having particle diameters between 1 and 50 nm were supportedon the surface of titanium oxide crystals in the obtained photocatalystmaterial.

Example 2 Cu-Supporting Photocatalyst Material Prepared by Wet Process

Copper nitrate trihydrate (Cu(NO₃)₂.3H₂O, prepared by Wako Pure ChemicalIndustries, Ltd., Special Grade) was diluted with distilled water, andthe concentration was adjusted to 2×10⁻⁵ mol/l. The titanium oxidefilter was immersed in the aqueous solution of copper nitrate, andallowed it to stand for 24 hours. By this operation, Cu was adsorbed onthe surface of titanium oxide until equilibrium adsorption was reached.After supporting Cu on the titanium oxide filter, it was washed withpure water. Thereafter, it was dried at 150° C. for 1 hour, andsubjected to heat treatment in the air at 450° C. for 2 hours. Since thesurface of Cu in the state subjected to heat treatment in the air was inthe oxidized state, it was reduced in a water-vapor atmosphere. Thetitanium oxide filter was packed in a quartz-glass tube, and wassubjected to reduction treatment using a 10-vol % hydrogen-argon mixedgas at 450° C. for 2 hours. It was confirmed by SEM observation thatfine Cu particles having particle diameters between 1 and 50 nm weresupported on the surface of titanium oxide crystals in the obtainedphotocatalyst material.

Example 3 Cu-Supporting Photocatalyst Material Prepared by PVD Method

A sputtering method was conducted using an RF magnetron sputteringapparatus (ULVAC, Inc., SH-350EL-T06). In the film-forming chamber, asubstrate supporting a titanium oxide photocatalyst of a columnar hollowstructure was placed facing a Cu target. As the target, a Cu targethaving target purity of 99.99% or above was used. The chamber wasevacuated to 10 Pa using an oil rotary pump. Thereafter, evacuation wasperformed using a turbo molecular pump to make the film-forming chamberhave a predetermined vacuum. Then, argon gas of a purity of 99.999% orabove was introduced to make the film-forming chamber have an argonatmosphere. At this time, the flow rate of the introduced gas and theopening of the main valve were adjusted to a predetermined argon gaspressure (sputtering pressure). Then, an electric power was impressed tothe Cu target from a DC power source to perform Cu sputtering, and whilerotating the disposed titanium oxide substrate at a rotation speed of 3rpm to make the surface thereof support fine Cu particles.

Since the purpose is to support fine Cu particles, not to form a Cufilm, a short-time treatment of 3 minutes was performed. It wasconfirmed by SEM observation that fine Cu particles having particlediameters between 1 and 50 nm were supported on the surface of titaniumoxide crystals in the obtained photocatalyst material.

Comparative Example 1

A titanium oxide substrate of a columnar hollow structure without theabove-described treatment for supporting fine Cu particles was madeComparative Example 1.

Comparative Example 2

A commercially available powdery photocatalyst material (produced byNippon Aerosol Co., Ltd., P-25) was made Comparative Example 2.According to surface observation using an SEM, this was composed oftitanium oxide particles having particle diameters between about 20 and30 nm.

<Method for Evaluating Properties>

For evaluating the performance of the photocatalyst, a decompositiontest for acetaldehyde, which is a harmful substance, was conducted. Inthe testing method, the prepared titanium oxide photocatalyst body(catalyst-supporting area: 75 mm×75 mm, titanium oxide supportingquantity: about 0.1 g) was first charged in a 20-L glass container, andafter replacing the interior of the container with artificial air,acetaldehyde gas was injected into the container so that theconcentration became 20 ppm. Next, a sterilization lamp of a wavelengthof 254 nm was radiated onto the titanium oxide photocatalyst body, andthe time required until the acetaldehyde concentration in the containerbecame 1 ppm or less was measured using a gas monitor. The surfaceobservation of the prepared titanium oxide photocatalyst body wasconducted using an SEM. The gas composition of the artificial air usedin the measurement (prepared by Taiyo Nippon Sanso Corporation) is 78%nitrogen, 21% oxygen, 0.9% argon, 0.03% carbonic acid gas (CO, CO₂,CH₄), and moisture for the balance.

The presence or absence of characteristic odor produced duringultraviolet radiation was judged by the sensory evaluation of 5 testers.The obvious occurrence of the characteristic odor was judged as“present”, no observation of the characteristic odor was judged as“absent”, and the observation of the characteristic odor for some extentbut not so significant as “present” was judged as “somewhat present”;and the results were collectively evaluated.

The results of property evaluation in each example and comparativeexample are shown in Table 2; and the results of the sensory test areshown in Table 3. TABLE 2 TIME OF ACETALDEHYDE ODOR PRODUCEDDECOMPOSITION DURING (TIME UNTIL 20 PPM TO 1 ULTRAVIOLET PPM OR LESS)RADIATION Example 1 6 min None Example 2 6 min None Example 3 8 min NoneComparative 15 min Yes Example 1 Comparative 28 min Yes Example 2

TABLE 3 Sensory evaluation of odor produced during ultraviolet radiationTester A B C D E Example 1 Absent Absent Absent Absent Absent Example 2Absent Absent Absent Absent Absent Example 3 Absent Absent Absent AbsentAbsent Comparative Present Present Present Present Present Example 1Comparative Present Present Present Present Present Example 2

The following is known from the results shown in Table 2.

It was confirmed by SEM observation that an aggregate consisting ofphotocatalyst crystal bodies, which were columnar hollow crystals havingheights between 3000 and 5000 nm and widths between 300 and 500 nm, wasformed in Comparative Example 1. The time required for lowering theconcentration of 20 ppm of acetaldehyde gas in a predetermined volumespace to 1 ppm or less, that is the decomposition time of acetaldehyde(hereafter referred to as “decomposition time of acetaldehyde”) was 15minutes, and it was shown that the required time for decomposition wasshortened to about one-second compared with the later-describedComparative Example 2, the decomposition efficiency was improved toabout twice, and even in the stage wherein the fine base-metal particlessupporting technique of the present invention had not applied, thedecomposition performance was already sufficiently higher than the priorart, and Comparative Example 1 had highly active photocatalysticfunctions. When ultraviolet rays were radiated, odor characteristic tothe TiO₂ photocatalyst was produced.

It was confirmed from SEM observation that a large number of titaniumoxide particles having particle diameters between 20 and 30 nm werepresent in Comparative Example 2, which is a powdery photocatalystmaterial. The decomposition time of acetaldehyde was 28 minutes. Whenultraviolet rays were radiated, odor characteristic to the TiO₂photocatalyst was produced.

In contrast to Comparative Examples 1 and 2, Examples 1 to 3 aretitanium oxide crystalline photocatalyst materials having columnarhollow structures, wherein fine Cu particles of particle diametersbetween 1 and 50 nm are supported on the surface of the titanium oxidecrystalline photocatalysts having columnar hollow structures byperforming a base-metal supporting treatment. The result of each examplewill be shown below.

Example 1 is a photocatalyst material wherein fine Cu particles aresupported on a titanium oxide photocatalyst having a columnar hollowstructure using a photo-precipitation method. It is predicted that theobtained photocatalyst material fine Cu particles of particle diametersbetween 1 and 50 nm are supported on the surface of a titanium oxidecrystals having a columnar hollow structure.

The decomposition time of acetaldehyde was 6 minutes, and compared with28 minutes of Comparative Example 2, the decomposition time could beshortened to one-fourth to one-fifth, the decomposition efficiency couldbe improved to 4 to 5 times or more, and the properties of prior artcould be very greatly improved.

Also in comparison with 15 minutes of Example 1, the decomposition timecould be shortened to about two-fifth, the decomposition efficiencycould be improved to about 2.5 times, the properties of titanium oxidephotocatalyst material having a columnar hollow structure could besignificantly improved, and it was demonstrated that Example 1 is aphotocatalyst material having very high decomposition performance andhighly active photocatalytic functions. When ultraviolet rays wereradiated, no odor characteristic to TiO₂ photocatalyst was produced.

Example 2 is a photocatalyst material wherein fine Cu particles aresupported on a titanium oxide photocatalyst having a columnar hollowstructure using a wet process including a reducing process. It ispredicted that the obtained photocatalyst material fine Cu particles ofparticle diameters between 1 and 50 nm are supported on the surface of atitanium oxide crystals having a columnar hollow structure.

The decomposition time of acetaldehyde was 6 minutes, and compared with28 minutes of Comparative Example 2, the decomposition time could beshortened to one-fourth to one-fifth, the decomposition efficiency couldbe improved to 4 to 5 times or more, and the properties of prior artcould be very greatly improved.

Also in comparison with 15 minutes of Example 1, the decomposition timecould be shortened to about two-fifth, the decomposition efficiencycould be improved to about 2.5 times, the properties of titanium oxidephotocatalyst material having a columnar hollow structure could besignificantly improved, and it was demonstrated that Example 1 is aphotocatalyst material having very high decomposition performance andhighly active photocatalytic functions. When ultraviolet rays wereradiated, no odor characteristic to TiO₂ photocatalyst was produced.

Example 3 is a photocatalyst material wherein fine Cu particles aresupported on a titanium oxide photocatalyst having a columnar hollowstructure using a sputtering method, which is one of PVD methods. It ispredicted that the obtained photocatalyst material fine Cu particles ofparticle diameters between 1 and 50 nm are supported on the surface of atitanium oxide crystals having a columnar hollow structure.

The decomposition time of acetaldehyde was 8 minutes, and compared with28 minutes of Comparative Example 2, the decomposition time could beshortened to one-third, the decomposition efficiency could be improvedto 3 times or more, and the properties of prior art could be verygreatly improved.

Also in comparison with 15 minutes of Example 1, the decomposition timecould be shortened to about a half, the decomposition efficiency couldbe improved to about twice, the properties of titanium oxidephotocatalyst material having a columnar hollow structure could besignificantly improved, and it was demonstrated that Example 3 is aphotocatalyst material having very high decomposition performance andhighly active photocatalytic functions. When ultraviolet rays wereradiated, no odor characteristic to TiO₂ photocatalyst was produced.

In Examples 1 to 3, although Cu was used as a supported base metal, itwas confirmed by experiments that the high activation of photocatalyticfunctions could be achieved even when Fe, Ni, Zn, Co V, Zr or Mn wassupported on the surface of the photocatalyst.

Although Cu was supported using a photo-precipitation method, a wetprocess, and a physical vapor deposition method in Examples 1 to 3, thesame effect could be obtained even when Cu was supported using othermethods, such as a chemical vapor deposition method, a spray pyrolysismethod, and a chemical precipitation method. This was confirmed byexperiments.

The evaluation of properties was conducted using not only acetaldehyde,but also other organic compounds, such as toluene, xylene, styrene andtrimethylamine, and it was confirmed that the base-metal supportedphotocatalyst material of the present invention had the samedecomposition performance and highly active photocatalytic functions forthese organic compounds equivalent to the case of acetaldehyde.

INDUSTRIAL APPLICABILITY

Since the photocatalyst material and the method for the preparationthereof according to the present invention is constituted as descriedabove, photocatalytic functions with extremely high activity can beachieved. Especially, according to the method for supporting a basemetal, this can be realized at low costs. Furthermore, since thephotocatalyst material is easy to handle without flying or dropping, itis easy to incorporate in an environmental purification device or thelike, the manufacturing costs can be reduced.

In addition, the photocatalyst material according to the presentinvention can reduce the characteristic odor produced during ultravioletradiation.

Moreover, since the photocatalyst material according to the presentinvention has significant effects in cleaning functions, antibacterialfunctions, deodorizing functions, antifouling functions and the like dueto photocatalytic functions of extremely high activity, it can be widelyapplied to various air conditional machinery and equipment, such as aircleaners, deodorizing equipment and cooling and heating systems, or toenvironmental purification equipment, such as water-clearing machinesand water quality purification equipment.

1. A photocatalyst material supported by a photocatalyst materialsupporting body for constituting a photocatalyst body, characterized inthat the particles of either one of a metal or a metallic compound aresupported by said photocatalyst material.
 2. A photocatalyst materialsupported by a photocatalyst material supporting body for constituting aphotocatalyst body, characterized in that the particles of either one ofa base metal or a base-metal compound are supported by saidphotocatalyst material.
 3. A photocatalyst material supported by aphotocatalyst material supporting body for constituting a photocatalystbody, characterized in that the particles of both a base metal and abase-metal compound are supported by said photocatalyst material.
 4. Thephotocatalyst material according to claim 2, characterized in that saidphotocatalyst is titanium oxide, and said base metal or base-metalcompound is at least one of Cu, Fe, Ni, Zn, Co, V, Zr, Mn, Sn, Cr, W,Mo, Nb, Ta, or the compounds thereof.
 5. The photocatalyst materialaccording to claim 2, characterized in that said photocatalyst materialis a photocatalyst material consisting of a base portion to be fixed onthe surface of the photocatalyst material supporting body or a baseportion fixed on the surface of the photocatalyst material supportingbody, and a columnar photocatalyst crystalline body extending from saidbase portion.
 6. The photocatalyst material according to claim 5,characterized in that said base portion consists of crystal nuclei orthe like, and the inside of said columnar photocatalyst crystalline bodyhas a hollow columnar structure.
 7. The photocatalyst material accordingto claim 6, characterized in that a structure consisting of finephotocatalyst particles in said photocatalyst crystalline body.
 8. Thephotocatalyst material according to claim 2, characterized in that whenacetaldehyde gas is decomposed using said photocatalyst materialconsisting of a supporting quantity of about 0.1 g supported on thephotocatalyst material supporting body having a catalyst supporting areaof 75 mm×75 mm, the time required for reducing the acetaldehyde gasconcentration in a glass container of a volume of 20 liter is 5 minutesor more and 10 minutes or less.
 9. A photocatalyst body comprising aphotocatalyst material supporting body, and the photocatalyst materialsupported on the photocatalyst material supporting body according toclaim
 2. 10. A method for producing a photocatalyst material comprisinga raw photocatalyst material preparing step for obtaining aphotocatalyst material that supports no base metals or no compoundsthereof (hereafter referred to as “raw photocatalyst material”), and abase-metal supporting step for supporting the fine particles of a basemetal or the compound thereof on the surface of the obtained rawphotocatalyst material; characterized in that said base-metal supportingstep comprises a solution treatment step for implementing treatment,such as immersing and applying, using a solution of a base-metalcompound to the raw photocatalyst material; and a ultraviolet treatmentstep for reducing and depositing the base metal or the compound thereofon the surface of the raw photocatalyst material by radiatingultraviolet rays on the photocatalyst material treated in said solutiontreatment step.
 11. A method for producing a photocatalyst materialcomprising a raw photocatalyst material preparing step for obtaining aphotocatalyst material that supports no base metals or no compoundsthereof, and a base-metal supporting step for supporting the fineparticles of a base metal or the compound thereof on the surface of theobtained raw photocatalyst material; characterized in that saidbase-metal supporting step comprises a solution treatment step forimplementing treatment, such as immersing and applying, using a solutionof a base-metal compound to the raw photocatalyst material; a dryingstep for drying the photocatalyst material treated in said solutiontreatment step; and a heat treatment step for heat-treating thephotocatalyst material treated in said drying step.
 12. The method forproducing a photocatalyst material according to claim 11, characterizedin further comprising, after said heat treatment step, a reduction stepfor reducing fine base metal particles in an oxidized state supported onthe surface of said photocatalyst material.
 13. A method for producing aphotocatalyst material comprising a raw photocatalyst material preparingstep for obtaining a photocatalyst material that supports no base metalsof no compounds thereof, and a base-metal supporting step for supportingthe fine particles of a base metal or the compound thereof on thesurface of the obtained raw photocatalyst material; characterized inthat said base-metal supporting step is a chemical vapor deposition stepfor supporting the fine particles of a base metal or a compound thereofon the surface of the raw photocatalyst material by a thermal CVDmethod, a plasma CVD method, or other chemical vapor deposition methods.14. A method for producing a photocatalyst material comprising a rawphotocatalyst material preparing step for obtaining a photocatalystmaterial that supports no base metals of no compounds thereof, and abase-metal supporting step for supporting the fine particles of a basemetal or the compound thereof on the surface of the obtained rawphotocatalyst material; characterized in that said base-metal supportingstep is a spray pyrolysis step for pyrolyzing a solution of a base metalcompound by spraying it on the surface of a heated raw photocatalystmaterial, and thereby the base metal or the compound thereof issupported on the surface of the raw photocatalyst material.
 15. A methodfor producing a photocatalyst material comprising a raw photocatalystmaterial preparing step for obtaining a photocatalyst material thatsupports no base metals or no compounds thereof, and a base-metalsupporting step for supporting the fine particles of a base metal or thecompound thereof on the surface of the obtained raw photocatalystmaterial; characterized in that said base-metal supporting stepcomprises a solution treatment step for implementing treatment, such asimmersing and applying, using a solution of a base-metal compound to theraw photocatalyst material; and a reducing agent adding step fordepositing a base metal or the compound thereof on the surface of theraw photocatalyst material by adding a reducing agent to thephotocatalyst material treated in said solution treatment step.
 16. Amethod for producing a photocatalyst material comprising a rawphotocatalyst material preparing step for obtaining a photocatalystmaterial that supports no base metals or no compounds thereof, and abase-metal supporting step for supporting the fine particles of a basemetal or the compound thereof on the surface of the obtained rawphotocatalyst material; characterized in that said base-metal supportingstep is a physical vapor deposition step for supporting the fineparticles of a base metal or a compound thereof on the surface of theraw photocatalyst material by a sputtering method, a vacuum vapordeposition method, or other vapor deposition methods.